Ventilation assembly and ventilation housing

ABSTRACT

A ventilation assembly of the present disclosure includes: an internal member being a tubular body having an opening at a first end portion and an opening at a second end portion; a gas-permeable membrane covering the opening at the first end portion of the internal member; and an external member being a tubular body having a bottom, the external member being joined to the internal member with the internal member inserted in the interior of the external member from the first end portion side, wherein the ventilation assembly is to be fixed to the projection of the housing with the projection inserted in the opening at the second end portion of the internal member to make an inner peripheral surface of the internal member and an outer peripheral surface of the projection abut each other, the ventilation assembly has a second space serving as a ventilation path connecting the gas-permeable membrane and the outside of the ventilation assembly in at least one selected from the inside of the internal member, the inside of the external member, and an interspace between the internal member and the external member joined together, and a total length of a height of the internal member and a shortest length in the second space from an outer periphery of the internal member at the first end portion to an end portion of the ventilation path on the outside side is 6.0 mm or more and 20 mm or less. The ventilation assembly of the present disclosure is excellent in moisture permeation performance.

TECHNICAL FIELD

The present invention relates to a ventilation assembly fixed to a housing when used and a ventilation housing including a ventilation assembly fixed.

BACKGROUND ART

Ventilation assemblies for ensuring ventilation between the inside and the outside of a housing, reducing pressure variation inside the housing, and so on are sometimes fixed to housings of in-vehicle electrical components such as lamps, inverters, converters, electronic control units (ECUs), battery packs, radars, and cameras and various electronic devices for home use, medical use, office use, etc. Ventilation assemblies are required to have, in addition to ventilation properties, various properties such as dust proofness for preventing entry of dust into housings, water proofness for preventing entry of water into housings, oil proofness for preventing entry of oil into housings, and CCT resistance for preventing entry of salt into housings depending on the specific electrical components, etc. to which the ventilation assemblies are fixed.

Patent Literature 1 discloses a ventilation assembly that can satisfy the ventilation properties and the various required properties. FIG. 30 shows the ventilation assembly disclosed in Patent Literature 1.

A ventilation assembly 101 shown in FIG. 30 includes an internal member 102 which is a tubular body having openings at both end portions 108 and 109, a gas-permeable membrane 103 covering the opening at the one end portion 108 of the internal member 102, and an external member 104 which is a tubular body having a bottom. The external member 104 is joined to the internal member 102 with the internal member 102 inserted in the interior of the external member 104 from the end portion 108 side. The external member 104 includes a projecting portion 106 projecting from an inner side 105 of a bottom portion in the direction along the central axis of the ventilation assembly 101. The projecting portion 106 abuts the gas-permeable membrane 103 disposed at the end portion 108 of the internal member 102. Since the projecting portion 106 abuts the gas-permeable membrane 103, the external member 104 and the gas-permeable membrane 103 are kept spaced apart from each other. Between the inner side 105 of the bottom portion of the external member 104 and the gas-permeable membrane 103 and between the outer peripheral surface of the internal member 102 and the inner peripheral surface of the external member 104, the ventilation assembly 101 has a space 107 serving as a ventilation path 115 connecting the exterior of the ventilation assembly 101 and the gas-permeable membrane 103.

The ventilation assembly 101 is fixed to a tubular projection 112 extending to project from the outer surface of a housing 111 and internally having a space 110 communicating the inside and the outside of the housing 111. Specifically, the projection 112 is inserted in the internal member 102 through the opening at the other end portion 109 of the internal member 102 to fix the ventilation assembly 101 to the projection 112. This allows ventilation between the inside and the outside of the housing 111 through the projection 112 and the ventilation assembly 101 with the ventilation assembly 101 fixed.

CITATION LIST Patent Literature

Patent Literature 1: JP 2003-336874 A

SUMMARY OF INVENTION Technical Problem

The present invention aims to provide a ventilation assembly fixed to a tubular projection extending to project from the outer surface of a housing and internally having a space communicating the inside and the outside of a housing, the ventilation assembly being excellent in moisture permeation performance.

Solution to Problem

The present invention provides a ventilation assembly to be fixed to a tubular projection extending to project from an outer surface of a housing and internally having a first space communicating the inside and the outside of the housing, the ventilation assembly including:

an internal member being a tubular body having an opening at a first end portion and an opening at a second end portion;

a gas-permeable membrane covering the opening at the first end portion of the internal member; and

an external member being a tubular body having a bottom, the external member being joined to the internal member with the internal member inserted in the interior of the external member from the first end portion side, wherein

the ventilation assembly is to be fixed to the projection with the projection inserted in the opening at the second end portion of the internal member to make an inner peripheral surface of the internal member and an outer peripheral surface of the projection abut each other,

the ventilation assembly has a second space serving as a ventilation path connecting the gas-permeable membrane and the outside of the ventilation assembly in at least one selected from the inside of the internal member, the inside of the external member, and an interspace between the internal member and the external member joined together, and

a total length of a height of the internal member and a shortest length in the second space from an outer periphery of the internal member at the first end portion to an end portion of the ventilation path on the outside side is 6.0 mm or more and 20 mm or less.

In another aspect, the present invention provides a ventilation housing including;

a housing; and

a ventilation assembly, wherein

the housing includes a tubular projection extending to project from an outer surface of the housing and internally having a first space communicating the inside and the outside of the housing,

the ventilation assembly is the above ventilation assembly of the present invention, and

the ventilation assembly is fixed to the projection with the projection inserted in the internal member through the opening at the second end portion of the internal member to make an inner peripheral surface of the internal member and an outer peripheral surface of the projection abut each other.

Advantageous Effects of Invention

According to a study by the present inventors, the ventilation assembly in which the total length of the height of the internal member and the shortest length in the second space from the outer periphery at the second end portion of the internal member to the end portion of the ventilation path on the outside side is controlled as described above exhibits excellent moisture permeation performance.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1A is a cross-sectional view schematically showing a ventilation assembly of a first embodiment.

FIG. 1B is a cross-sectional view schematically showing the ventilation assembly of the first embodiment.

FIG. 2 is an exploded perspective view schematically showing the ventilation assembly of the first embodiment.

FIG. 3A is a cross-sectional view schematically showing a ventilation assembly of a second embodiment.

FIG. 3B is a cross-sectional view schematically showing the ventilation assembly of the second embodiment.

FIG. 4 is an exploded perspective view schematically showing the ventilation assembly of the second embodiment.

FIG. 5A is a cross-sectional view schematically showing a ventilation assembly of a third embodiment.

FIG. 5B is a cross-sectional view schematically showing the ventilation assembly of the third embodiment.

FIG. 6 is an exploded perspective view schematically showing the ventilation assembly of the third embodiment.

FIG. 7A is a cross-sectional view schematically showing a ventilation assembly of a fourth embodiment.

FIG. 7B is a cross-sectional view schematically showing the ventilation assembly of the fourth embodiment.

FIG. 8 is an exploded perspective view schematically showing the ventilation assembly of the fourth embodiment.

FIG. 9A is a cross-sectional view schematically showing a ventilation assembly of a fifth embodiment.

FIG. 9B is a cross-sectional view schematically showing the ventilation assembly of the fifth embodiment.

FIG. 10 is an exploded perspective view schematically showing the ventilation assembly of the fifth embodiment.

FIG. 11A is a cross-sectional view schematically showing a ventilation assembly of a sixth embodiment.

FIG. 11B is a cross-sectional view schematically showing the ventilation assembly of the sixth embodiment.

FIG. 12 is an exploded perspective view schematically showing the ventilation assembly of the sixth embodiment.

FIG. 13A is a perspective view of a ventilation assembly produced in EXAMPLES.

FIG. 13B is a perspective view schematically showing an external member included in the ventilation assembly of FIG. 13A.

FIG. 14A is a plan view schematically showing a housing lid used to evaluate the moisture permeation performance (moisture permeation rate) of a ventilation housing.

FIG. 14B is a schematic view showing a cross-section of the housing lid of FIG. 14A.

FIG. 15A is a perspective view of a ventilation assembly produced in EXAMPLES.

FIG. 15B is a perspective view schematically showing an external member included in the ventilation assembly of FIG. 15A.

FIG. 16 is a graph on which a relation between moisture permeation rates and ventilation distances is plotted for Examples 1 to 5 and Comparative Example 1.

FIG. 17A is a perspective view of a ventilation assembly produced in EXAMPLES.

FIG. 17B is a perspective view schematically showing an external member included in the ventilation assembly of FIG. 17A.

FIG. 18A is a perspective view of a ventilation assembly produced in EXAMPLES.

FIG. 18B is a perspective view schematically showing an external member included in the ventilation assembly of FIG. 18A.

FIG. 19A is a perspective view of a ventilation assembly produced in EXAMPLES.

FIG. 19B is a perspective view schematically showing an external member included in the ventilation assembly of FIG. 19A.

FIG. 20 shows images used to measure areas S2 _(min) of ventilation assemblies produced in EXAMPLES.

FIG. 21 shows images used to measure areas S2 _(out) of ventilation assemblies produced in EXAMPLES.

FIG. 22 shows post-binarization images used to measure areas S2 _(out) of ventilation assemblies produced in EXAMPLES.

FIG. 23 is a graph on which a relation between ratios S2 _(out)/S1 and moisture permeation rates is plotted for Examples 6 to 10.

FIG. 24 is a schematic view for illustrating a pullout test for an internal member.

FIG. 25 is a graph showing an SS curve obtained in a pullout test for an internal member.

FIG. 26 is a graph on which a relation between ratios H1/H2 and pullout forces is plotted for Reference Examples in which internal members were pulled apart without being broken in a pullout test for the internal members.

FIG. 27 is a graph showing SS curves obtained in a pullout test for external members.

FIG. 28 is a graph on which a relation between insertion depths of external members and pullout forces is plotted for Reference Examples.

FIG. 29 is a graph on which a relation between insertion depths of external members and moisture permeation rates is plotted for Examples 2 to 4.

FIG. 30 is a cross-sectional view schematically showing an example of a conventional ventilation assembly.

DESCRIPTION OF EMBODIMENTS

A ventilation assembly of a first aspect of the present disclosure is to be fixed to a tubular projection extending to project from an outer surface of a housing and internally having a first space communicating the inside and the outside of the housing, the ventilation assembly including:

an internal member being a tubular body having an opening at a first end portion and an opening at a second end portion;

a gas-permeable membrane covering the opening at the first end portion of the internal member; and

an external member being a tubular body having a bottom, the external member being joined to the internal member with the internal member inserted in the interior of the external member from the first end portion side, wherein

the ventilation assembly is to be fixed to the projection with the projection inserted in the opening at the second end portion of the internal member to make an inner peripheral surface of the internal member and an outer peripheral surface of the projection abut each other,

the ventilation assembly has a second space serving as a ventilation path connecting the gas-permeable membrane and the outside of the ventilation assembly in at least one selected from the inside of the internal member, the inside of the external member, and an interspace between the internal member and the external member joined together, and

a total length of a height of the internal member and a shortest length in the second space from an outer periphery of the internal member at the first end portion to an end portion of the ventilation path on the outside side is 6.0 mm or more and 20 mm or less.

According to a second aspect of the present disclosure, in the ventilation assembly of the first aspect,

when the ventilation assembly is observed in a direction perpendicular to a central axis of the ventilation assembly, a length of a portion of the internal member in a direction along the central axis is 6.0 mm or more and 8.0 mm or less, the portion being covered by the external member.

According to a third aspect of the present disclosure, in the ventilation assembly of the first or second aspect,

the external member has a through hole penetrating a bottom portion of the external member and/or a peripheral wall of the external member and connecting the outside of the ventilation assembly and the second space, and

the shortest length in the second space extends through the through hole.

According to a fourth aspect of the present disclosure, in the ventilation assembly of the third aspect,

the through hole is arranged through both the bottom portion of the external member and the peripheral wall of the external member.

According to a fifth aspect of the present disclosure, in the ventilation assembly of any one of the first to fourth aspects,

the external member and/or the internal member has a locking mechanism detachably joining the external member and the internal member together.

A ventilation housing of a sixth aspect of the present disclosure includes:

a housing; and

a ventilation assembly, wherein

the housing includes a tubular projection extending to project from an outer surface of the housing and internally having a first space communicating the inside and the outside of the housing,

the ventilation assembly is the ventilation assembly according to any one of the first to five aspects, and

the ventilation assembly is fixed to the projection with the projection inserted in the internal member through the opening at the second end portion of the internal member to make an inner peripheral surface of the internal member and an outer peripheral surface of the projection abut each other.

According to a seventh aspect of the present disclosure, in the ventilation housing of the sixth aspect,

a ratio S2 _(min)/S1 between an area Si of a cross-section of the first space taken along a plane perpendicular to a central axis of the projection and a smallest total area S2 _(min) determined by comparison of values of different total areas determined at different distances from the gas-permeable membrane is 1.0 or more, the total areas each being determined for a cross-section(s) of the second space taken along a plane perpendicular to a ventilation direction in the ventilation path, the cross-section(s) being located at a certain distance from the gas-permeable membrane.

According to an eighth aspect of the present disclosure, in the ventilation housing of the sixth or seventh aspect,

a ratio S2 _(out)/S1 between an area Si of a cross-section of the first space taken along a plane perpendicular to a central axis of the projection and a total area S2 _(out) of a plane consisting of a cross-section(s) of the second space taken at a position(s) where the second space is the narrowest when the second space is observed from the second end portion side along a central axis of the ventilation assembly is 1.0 or more.

Embodiments of the present invention will be described hereinafter with reference to the accompanying drawings. The following description is not intended to limit the present invention to particular embodiments.

First Embodiment

FIGS. 1A and 1B show a ventilation assembly 1A of a first embodiment. FIG. 1B shows a cross-section B-B of the ventilation assembly 1A shown in FIG. 1A. FIG. 1A shows a cross-section A-O-A of the ventilation assembly 1A shown in FIG. 1B. “O” in FIG. 1B indicates the central axis of the ventilation assembly 1A. FIGS. 1A and 1B show a state where the ventilation assembly 1A is fixed to a projection 52 of a housing 51, in other words, the vicinity of the projection 52 of the housing 51 in a ventilation housing including the ventilation assembly 1A fixed to the projection 52. FIG. 2 shows an exploded perspective view of the ventilation assembly 1A shown in FIGS. 1A and 1B. As shown in FIGS. 1A, 1B, and 2, the ventilation assembly 1A is fixed to the tubular projection 52 extending to project from an outer surface 53 of the housing 51 and internally having a first space 59 communicating the inside and the outside of the housing 51.

The ventilation assembly 1A includes an internal member 2, a gas-permeable membrane 3, and an external member 4. The internal member 2 is a tubular body having an opening 12A at an end portion 11A and an opening 12B at an end portion 11B that is opposite to the end portion 11A. The internal member 2 has an open tubular structure in which both end portions have openings. The gas-permeable membrane 3 is disposed at the one end portion 11A of the internal member 2 so as to cover the opening 12A at the end portion 11A. The external member 4 is a tubular body having a bottom. The external member 4 has a closed tubular structure in which one end portion 42 has an opening and the other end portion has a closed opening closed by a bottom portion 32. The external member 4 is joined to the internal member 2 with the internal member 2 inserted in the interior of the external member 4 from the end portion 11A side where the gas-permeable membrane 3 is disposed. Here, the interior of the external member 4 refers to a space surrounded by the opening of the external member 4 and an inner peripheral surface 31. The external member 4 covers the gas-permeable membrane 3 so as to function as a cover that protects the gas-permeable membrane 3 from foreign matters such as dust and water coming from the outside.

The ventilation assembly 1A has a second space 5 serving as a ventilation path connecting the gas-permeable membrane 3 and the outside of the ventilation assembly 1A. The ventilation assembly 1A has a space 5 a, which is a part of the second space 5, between an outer peripheral surface 40 of the external member 4 joined to the internal member 2 and an inner peripheral surface 13 of the internal member 2. The ventilation assembly 1A also has the space 5 a between the internal member 2 and the external member 4 joined together, more specifically, between the inner peripheral surface 31 of the external member 4 and an outer peripheral surface 19 of the internal member 2. In the ventilation assembly 1A, an inner side 33 of the bottom portion 32 of the external member 4 and the gas-permeable membrane 3 are spaced apart from each other. The ventilation assembly 1A has a space 5 b, which is a part of the second space 5, between the inner side 33 and the gas-permeable membrane 3 spaced apart from each other. The second space 5 (and the space 5 a) communicates to the outside of the ventilation assembly 1A at a ventilation hole 17 which is an end portion (from the standpoint of the space 5 a, an end portion on the side opposite to the gas-permeable membrane 3 side) of the ventilation path on the outside side of the ventilation assembly 1A. The term “ventilation path” refers to a route through which gas can move between the gas-permeable membrane and the outside of the ventilation assembly. The term “ventilation path” refers to, for example, a gas flow route allowing air having permeated through the gas-permeable membrane 3 and reached the space 5 b to pass through the space 5 b and then the space 5 a and eventually reach the outside of the ventilation assembly 1A. Therefore, such a space as the space 5 a can be a “ventilation path” not only when located between the internal member 2 and the external member 4 joined together but also when located inside the internal member 2 or the external member 4. It should be noted that the ventilation path is determined for the ventilation assembly obtained when the internal member 2 is inserted as deep in the external member 4 as possible.

The ventilation assembly 1A is fixed to the projection 52 of the housing 51 with the projection 52 inserted in the internal member 2 through the opening 12B at the other end portion 11B of the internal member 2 to make the inner peripheral surface 13 of the internal member 2 and an outer peripheral surface 58 of the projection 52 abut each other. The projection 52 is inserted in a through hole 14 of the internal member 2 to fix the ventilation assembly 1A. The through hole 14 is a space connecting the end portions 11A and 11B and surrounded by the inner peripheral surface 13 of the internal member 2. In a ventilation housing including the ventilation assembly 1A fixed to the projection 52, ventilation between the inside and the outside of the housing 51 can be ensured through the first space 59 in the interior of the projection 52, the through hole 14 of the internal member 2, the gas-permeable membrane 3, and the second space 5, and the ventilation hole 17.

An area S1 of a cross-section of the first space 59 taken along a plane perpendicular to the central axis of the projection 52 may be 5 mm² or more and 60 mm² or less. The lower limit of the area S1 may be 10 mm² or more, 12 mm² or more, 14 mm² or more, or even 16 mm² or more. The upper limit of the area S1 may be 50 mm² or less, 40 mm² or less, 30 mm² or less, or even 20 mm² or less. The central axis of the projection 52 commonly coincides with the central axis O of the ventilation assembly 1A. The central axis O of the ventilation assembly 1A is, more specifically, the central axis of the internal member 2.

A thickness T1 of the internal member 2 at the one end portion 11A may be 1.0 mm or more and 3.0 mm or less, the thickness T1 being the distance between the inner peripheral surface 13 and the outer peripheral surface 19. The lower limit of the thickness T1 may be 1.1 mm or more, 1.2 mm or more, or even 1.3 mm or more. The upper limit of the thickness T1 may be 2.9 mm or less, 2.8 mm or less, or even 2.7 mm or less. The internal member 2 having a thickness T1 within these ranges ensures sufficient strength of the internal member 2 while allowing a reduction in the height of the ventilation assembly 1. For example, breaking, tearing, and the like of the internal member 2 can be prevented at the time of joining the external member 4 to the internal member 2. It should be noted that the thickness T1 is determined for the internal member 2 in which the projection 52 has not been inserted.

The internal member 2 of the first embodiment has a thin portion 15 having a decreased thickness T1 and extending from the end portion 11B from which the projection 52 is inserted at the time of fixation of the ventilation assembly lA to a given height in the direction along the central axis O. Moreover, the internal member 2 has a step 16 at the boundary between the thin portion 15 and the rest of the internal member 2. The step 16 is located farther from the outer surface 53 of the housing 51 than the end portion 42 of the external member 4 on the opening side is (the step 16 is located on the upper side of the ventilation assembly 1A with respect to the end portion 42). However, the position of the step 16 is not limited to this example. When the internal member 2 has the thin portion 15, it is easier to insert the projection 52 of the housing 51 in the ventilation assembly 1A. This effect is particularly advantageous when the internal member 2 has a small inner diameter, in other words, when it is difficult for the end portion 11B of the internal member 2 to stretch at the time of insertion of the projection 52. The internal member 2 does not have the thin portion 15 on the end portion 11A side where the gas-permeable membrane 3 is disposed, and that can prevent an inclination of the external member 4 and the internal member 2 to each other at the time of joining the members 2 and 4 together and an inclination of the internal member 2 at the time of inserting the projection 52 of the housing 51. This effect is particularly advantageous when the internal member 2 has a small thickness T1. In the example shown in FIGS. 1A, 1B, and 2, the peripheral surface of the thin portion 15 and the outer peripheral surface 19 are connected at the step 16 by a plane perpendicular to the central axis O. The plane connecting the peripheral surface of the thin portion 15 and the outer peripheral surface 19 at the step 16 may be inclined to the direction perpendicular to the central axis O.

In the ventilation assembly 1A, a shortest length L1 in the second space 5 from an outer periphery 24 of the internal member 2 at the one end portion 11A to the end portion (the ventilation hole 17) of the ventilation path on the outside side of the ventilation assembly 1A may be more than 0 mm and less than 10 mm. The lower limit of the shortest length L1 may be 1.0 mm or more, 2.0 mm or more, or even 3.0 mm or more. The upper limit of the shortest length L1 may be 9.0 mm or less, 8.0 mm or less, or even 7.0 mm or less. It should be noted that the position of the ventilation hole 17 is determined by a surface of the external member 4 on the outer periphery side. In the present embodiment, the ventilation hole 17 is located at the same height as a plane of the end portion 42 of the external member 4 on the opening side. It should be noted that the length L1 is determined when the internal member 2 is inserted as deep in the external member 4 as possible.

A height H1 of the internal member 2 may be 6.0 mm or more and 10 mm or less, the height H1 being the distance between the end portions 11A and 11B of the internal member 2 in the direction along the central axis O. The upper limit of the height H1 may be 9.5 mm or less, 9.0 mm or less, or even 8.5 mm or less. The lower limit of the height H1 may be 6.5 mm or more, 7.0 mm or more, or even 7.5 mm or more.

A total length of the height H1 and the length L1 is 6.0 mm or more and 20 mm or less. The upper limit of the total length may be 18 mm or less, 17 mm or less, or even 16 mm or less. The lower limit of the total length may be 8.0 mm or more, 9.0 mm or more, or even 10 mm or more.

The internal member 2 and the projection 52 of the first embodiment are each in the shape of a cylinder. Because the material of the internal member 2 is commonly an elastic body, the inner peripheral surface 13 of the internal member 2 commonly has a diameter equal to or smaller than the diameter of the outer peripheral surface 58 of the projection 52. It should be noted that the elastic modulus of the elastic body forming the internal member 2 and/or the diameter of the inner peripheral surface 13 of the internal member 2 can be controlled, for example, in consideration of ease of insertion of the projection 52 into the internal member 2, sealing properties between the housing 51 and the ventilation assembly 1A, and the like. The shape of the internal member 2 which is a tubular body and the shape of the tubular projection 52 are not limited to a cylinder.

The inner diameter of the cylindrical internal member 2 is, for example, 6.0 to 8.0 mm. Half the value obtained by subtracting the inner diameter of the cylindrical internal member 2 from the outer diameter thereof corresponds to the thickness T1.

The external member 4 is in the shape of a cylinder having a bottom. When the external member 4 is observed along the central axis O, a portion of a peripheral wall 37 of the external member 4 projects toward the interior of the external member 4, more specifically, toward the central axis O. As the peripheral wall 37 projects in the above manner, the external member 4 includes, on the outer peripheral surface 40, a plurality of grooves 41 (41A, 41B, 41C, and 41D) extending along the central axis O. In the example shown in FIGS. 1A, 1B, and 2, the grooves 41 are provided at regular intervals in the peripheral direction of the external member 4 when observed along the central axis O, and the grooves 41 extend from the end portion 42 of the external member 4 on the opening side to the bottom portion 32. In the external member 4, the thickness of the peripheral wall 37 at each of groove 41 portions and that at each of portions other than the groove 41 portions are substantially uniform. However, the positions which are on the outer peripheral surface 40 and where the grooves 41 are provided, the intervals between the adjacent grooves 41, the directions in which the grooves 41 extend, and zones where the grooves 41 extend and which are present between the end portion 42 and the bottom portion 32 of the external member 4 are not limited to those in the above example. The thickness of the peripheral wall 37 at each groove 41 portion and that at each portion other than the groove 41 portions may be different.

At the groove 41 portions, the inner peripheral surface 31 of the external member 4 coincides with the peripheral surface of a virtual column A having the central axis O as its central axis. The internal member 2 and the external member 4 are joined to each other by making the outer peripheral surface 19 and the inner peripheral surface 31 at the groove 41 portions abut each other. Because the material of the internal member 2 is commonly an elastic body, the virtual column A commonly has a diameter equal to or smaller than the diameter of the outer peripheral surface 19. Gaps 6A between the inner peripheral surface 31 of the external member 4 at the portions other than the groove 41 portions and the outer peripheral surface 19 of the internal member 2 are each a part of the space 5 a. The lower end portion (open end) of the gap 6A and that of the space 5 a form the ventilation hole 17. In the example shown in FIGS. 1A, 1B, and 2, the outer peripheral surface 19 of the internal member 2 does not have a protruding portion projecting from the surface 19. The outer peripheral surface 19 forms the entire peripheral surface of the column in the peripheral direction of the surface 19. In the example shown in FIGS. 1A, 1B, and 2, the number of the gaps 6A and that of the ventilation holes 17 are four. In the first embodiment, the number of the gaps 6A and that of the ventilation holes 17 are required to be one or two or more and may be two to eight or even three to six.

When the ventilation assembly 1A is observed in the direction perpendicular to the central axis O, a length D8 of a portion of the internal member 2 in the direction along the central axis O, the portion being covered by the external member 4, may be, for example, 3.5 mm or more and 9.5 mm or less or may be 6.0 mm or more and 8.0 mm or less. The lower limit of the length D8 may be 4.0 mm or more, 4.5 mm or more, or even 5.0 mm or more. The upper limit of the length D8 may be 9.0 mm or less, 8.5 mm or less, or even 8.0 mm or less. When the length D8 is in these ranges, the internal member 2 and the external member 4 are more reliably joined together and the external member 4 is unlikely to drop from the internal member 2, for example, at the time of fixation of the ventilation assembly 1A to the projection 52 of the housing 51. Moreover, sufficient moisture permeation performance can be ensured. Furthermore, entry of foreign matters such as dust and water from the outside of the ventilation assembly 1A into the second space 5 can be reduced. It should be noted that the length D8 is determined when the internal member 2 is inserted as deep in the external member 4 as possible.

For the internal member 2 and the external member 4 joined by making them abut each other, a length (inside-outside contact length) D4 in the direction along the central axis O is, for example, 4.0 to 8.0 mm, the length D4 of a portion where the internal member 2 and the external member 4 abut each other, more specifically, the length D4 of a portion where the outer peripheral surface 19 of the internal member 2 and the inner peripheral surface 31 of the external member 4 at the groove 41 portion abut each other. When the length D4 is in these ranges, the internal member 2 and the external member 4 are more reliably joined together and the external member 4 is unlikely to drop from the internal member 2, for example, at the time of fixation of the ventilation assembly 1A to the projection 52 of the housing 51. In the example shown in FIGS. 1A, 1B, and 2, a portion of the internal member 2, the portion abutting the inner peripheral surface 31 of the external member 4, extends in the direction along the central axis O from the end portion 11A where the gas-permeable membrane 3 is disposed to the step 16, in other words, to the lower end of the portion other than the thin portion 15. The portion of the internal member 2, the portion abutting the inner peripheral surface 31, spans the entire outer peripheral surface 19 in the peripheral direction.

A distance D6 in the direction along the central axis O and between the end portion (lower end) 42 on the opening side of the external member 4 and the end portion 11B of the internal member 2 is, for example, 0 to 3.0 mm, and may be 0.2 to 2.0 mm or even 0.4 to 1.0 mm. When the distance D6 is in these ranges, the internal member 2 and the external member 4 are more firmly joined together. It should be noted that the distance D6 is determined when the internal member 2 is inserted as deep in the external member 4 as possible.

The external member 4 includes two or more second projecting portions 34 projecting from the inner side 33 of the bottom portion 32 in the direction along the central axis O. Each of the second projecting portions 34 also projects from the inner peripheral surface 31 of the external member 4 toward the central axis O when observed along the central axis O. In a state where the external member 4 and the internal member 2 are joined together, the inner side 33 of the bottom portion 32 of the external member 4 and the gas-permeable membrane 3 are kept spaced apart from each other by making the second projecting portions 34 and the end portion 11A of the internal member 2 abut each other. The second projecting portions 34 may be provided in such a manner that in a state where the external member 4 and the internal member 2 are joined together, the second projecting portions 34 abut the gas-permeable membrane 3 or abut both the internal member 2 and the gas-permeable membrane 3.

A height H3 of the ventilation assembly 1A is, for example, 6.0 mm or more and 12 mm or less, the height H3 being the distance between a virtual plane being perpendicular to the central axis O and passing through the lowermost point in the ventilation assembly 1A and a virtual plane being perpendicular to the central axis O and passing through the uppermost point in the ventilation assembly 1A. The upper limit of the height H3 may be 11 mm or less, 10.5 mm or less, or even 10 mm or less. The lower limit of the height H3 may be 6.5 mm or more, 7.0 mm or more, or even 7.5 mm or more. It should be noted that the height H3 is determined when the internal member 2 is inserted as deep in the external member 4 as possible. In the example shown in FIGS. 1A, 1B, and 2, the lowermost point is located at the end portion 11B of the internal member 2, and the uppermost point is located at an outer side 35 of the bottom portion 32 of the external member 4.

In a state where the ventilation assembly 1A is fixed to the projection 52 of the housing 51, a ratio S2 _(min)/S1 of an area S2 _(min) of a cross-section(s) of the second space 5 to the area S1 of the cross-section of the first space 59 is, for example, 0.8 or more. The lower limit of the ratio S2 _(min)/S1 may be 1.0 or more, 1.1 or more, 1.2 or more, 1.3 or more, or even 1.4 or more. The upper limit of the ratio S2 _(min)/S1 is, for example, 3.0 or less and may be 2.5 or less or even 2.0 or less. The ventilation assembly and the ventilation housing having a ratio S2 _(min)/S1 in the above range are excellent in ventilation properties and/or moisture permeation performance. The area S1 is the area of the cross-section of the first space 59 taken along a plane perpendicular to the central axis of the projection 52. The area S2 _(min) is a smallest total area determined by comparison of values of different total areas determined at different distances from the gas-permeable membrane is 1.0 or more, the total areas each being determined for a cross-section(s) of the second space 5 taken along a plane perpendicular to a ventilation direction in the ventilation path, the cross-section(s) being located at a certain distance from the gas-permeable membrane. The term “ventilation path” refers to a path through which gas can move between the gas-permeable membrane and the outside of the ventilation assembly. The term “ventilation direction” refers to the direction in which gas should go at a particular position in the second space regarded as the ventilation path. Thus, the ventilation direction varies depending on the position in the second space. The expression “total area determined for cross-sections located at a certain distance from the gas-permeable membrane” is based on the viewpoint that the sum of areas of cross-sections of the second space 5 taken at a group of positions to which the distance (in the case of a point-symmetric gas-permeable membrane, the distance from the center of the gas-permeable membrane) from the gas-permeable membrane is the same is regarded as a total area. Of different total areas determined at different distances in such a manner, a total area of a cross-section(s) taken at a position(s) where the total area value is the smallest is the area S2 _(min). The area S2 _(min) is determined when the internal member 2 is inserted as deep in the external member 4 as possible. In the example shown in FIGS. 1A, 1B, and 2, the cross-sections whose areas compose the area S2 _(min) are each surrounded by the second projecting portion 34, a peripherally end portion 46 of a portion which is included in the groove 41 and where the internal member 2 and the external member 4 abut each other, the inner side 33 of the bottom portion 32 of the external member 4, and the end portion 11A of the internal member 2 (refer to a cross-section 47 in FIG. 2). FIG. 2 shows a part of the cross-sections whose areas compose the area S2 _(min) (only the cross-section 47 located between one second projecting portion 34 and one end portion 46). Because the cross-sections whose areas compose the area S2 _(min) are present between four second projecting portions 34 and eight end portions 46, eight times the area of the cross-section 47 corresponds to the area S2 _(min). The area S2 _(min) can be evaluated, for example, by a method described in EXAMPLES.

In a state where the ventilation assembly 1A is fixed to the projection 52 of the housing 51, a ratio S2 _(out)/S1 of an area S2 _(out) of a cross-section(s) of the second space 5 to the area S1 of the cross-section of the first space 59 is, for example, 0.8 or more, and may be 1.0 or more, 1.2 or more, 1.3 or more, 1.5 or more, 1.8 or more, 2.0 or more, or even 2.2 or more. The upper limit of the ratio S2 _(out)/S1 is, for example, 4.0 or less and may be 3.0 or less. The ventilation assembly and the ventilation housing having a ratio S2 _(out)/S1 in the above range are excellent in ventilation properties and/or moisture permeation performance. The area S2 _(out) is a total area of a plane consisting of a cross-section(s) of the second space 5 taken at a position(s) where the second space 5 within the observable range is the narrowest when the second space 5 is observed from the other end portion 11B side along the central axis of the ventilation assembly 1A. The area S2 _(out) is determined when the internal member 2 is inserted as deep in the external member 4 as possible. In the example shown in FIGS. 1A, 1B, and 2, the cross-sections whose areas compose the area S2 _(out) are each surrounded by the inner peripheral surface 31 of the external member 4 and the outer peripheral surface 19 of the internal member 2 (refer to a cross-section 48 in FIG. 1B). FIG. 1B shows a part of the cross-sections whose areas compose the area S2 _(out) (only the cross-section 48 located between a pair of the adjacent grooves 41C and 41D). Because the cross-sections whose areas compose the area S2 _(out) are located between the four grooves 41, four times the area of the cross-section 48 corresponds to the area S2 _(out). The area S2 _(out) can be evaluated, for example, by a method described in EXAMPLES.

Resins, such as polyamide, polycarbonate, and polybutylene terephthalate, having a relatively high hygroscopicity are sometimes included in housings of electrical components and electronic devices. A housing including any of such resins absorbs surrounding water vapor. The absorbed water vapor is emitted by heat from a heat source inside the housing or heat from the outside, such as sunlight, and a portion of the emitted water vapor remains inside the housing. It is desirable that the water vapor remaining inside the housing be immediately discharged to the outside of the housing through the projection 52 and the ventilation assembly 1A in order to prevent fogging inside the housing. The ventilation assembly and/or ventilation housing having excellent moisture permeation performance, for example, can reduce fogging inside the housing and promote removal of fogging inside the housing.

A height H2 of the projection 52 being the distance in the direction along the central axis O from the outer surface 53 of the housing 51 to the front end 54 of the projection 52 is, for example, 5.0 to 12 mm and may be 4.0 mm or more and 8.0 mm or less.

A ratio H1/H2 of the height H1 of the internal member 2 to the height H2 of the projection 52 may be 1.00 or more and 1.70 or less. The lower limit of the ratio H1/H2 may be more than 1.00, 1.02 or more, 1.04 or more, 1.06 or more, 1.08 or more, or even 1.10 or more. The upper limit of the ratio H1/H2 may be 1.60 or less, 1.50 or less, 1.40 or less, 1.30 or less, 1.25 or less, 1.22 or less, 1.20 or less, 1.18 or less, 1.16 or less, or even 1.14 or less. The ventilation assembly and the ventilation housing having a ratio H1/H2 in the above range can effectively reduce dropping of the ventilation assembly from the projection of the housing. When the ventilation assembly 1A is used, the projection 52 is inserted in the ventilation assembly 1A through the opening 12B at the other end portion 11B of the internal member 2. The ratio H1/H2 is determined for the ventilation assembly 1A obtained when the projection 52 is inserted as deep in the internal member 2 as possible.

In a state where the internal member 2 is fixed to the projection 52, a length D5 corresponding to the height of a portion of the internal member 2 is, for example, 4.0 to 8.0 mm, the portion covering the projection 52. When the length D5 is in these ranges, the ventilation assembly 1A is unlikely to drop from the projection 52 of the housing 51.

In the case where the internal member 2 is fixed to the projection 52, the distance between the outer surface 53 of the housing 51 and the end portion 42 of the external member 2 on the opening side is, for example, 0.5 mm or more and 4 mm or less. In the case where the above distance is in this range, an appropriate gas permeation amount can be ensured while dropping of the ventilation assembly 1A from the projection 52 of the housing 51 is prevented.

The gas-permeable membrane 3 is a membrane that allows gas (typically air) to permeate therethrough in its thickness direction and that prevents foreign matters from permeating therethrough. Therefore, the ventilation assembly 1A ensures ventilation between the inside and the outside of the housing 51 and can prevent entry of foreign matters such as dust, water, oil, and salt into the inside of the housing 51. In the first embodiment, the shape of the gas-permeable membrane 3 is a circle. However, the shape of the gas-permeable membrane 3 is not limited to a circle and can be selected according to the shape of a portion which is included in the internal member 2 and where the gas-permeable membrane 3 is disposed. The shape of the gas-permeable membrane 3 may be, for example, a polygon.

In the first embodiment, the gas-permeable membrane 3 is disposed on the end face of the end portion 11A of the internal member 2. However, in the ventilation assembly and the ventilation housing of the present invention, the position where the gas-permeable membrane 3 is disposed is not limited to the end face of the end portion 11A as long as the gas-permeable membrane 3 covers the opening 12A at the end portion 11A.

A woven fabric, non-woven fabric, mesh, or net formed of a resin or metal or a porous resin membrane can be used as the gas-permeable membrane 3. However, the gas-permeable membrane 3 is not limited as long as the gas-permeable membrane 3 allows gas to permeate therethrough and can prevent foreign matters such as liquid from permeating therethrough. In the first embodiment, the gas-permeable membrane 3 used is a laminate of a porous resin membrane and a gas-permeable reinforcing layer. The reinforcing layer can improve the strength of the gas-permeable membrane 3. The porous resin membrane is, for example, a porous body which is formed of a fluorine resin or polyolefin and which can be manufactured by a commonly-known stretching or extraction technique. Examples of the fluorine resin include polytetrafluoroethylene (PTFE), polychlorotrifluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, and tetrafluoroethylene-ethylene copolymer. Examples of the monomer forming the polyolefin include ethylene, propylene, 4-methylpentene-1,1-butene, and a polyolefin that is a homopolymer or copolymer of any of these monomers can be used as the gas-permeable membrane 3. A porous nanofiber film including polyacrylonitrile, nylon, or polylactic acid may be used as the gas-permeable membrane 3. A porous PTFE body capable of ensuring gas permeability with a small area and having a high ability to prevent entry of foreign matters into the inside of the housing 51 is particularly preferably used as the gas-permeable membrane 3. The average pore diameter of the porous PTFE body is preferably 0.01 μm or more and 10 μm or less. The reinforcing layer is formed of, for example, a woven fabric, non-woven fabric, mesh, net, sponge, foam, or porous body formed of a resin or metal. The porous resin membrane and the reinforcing layer can be laminated by a method such as adhesive lamination, thermal lamination, heat welding, ultrasonic welding, and bonding using an adhesive.

The gas-permeable membrane 3 may have been subjected to a liquid-repellent treatment. The liquid-repellent treatment of the gas-permeable membrane 3 can be performed by applying a liquid-repellent agent containing a substance having a small surface tension to the gas-permeable membrane and drying the coating film formed by the application. As the substance described above, the liquid-repellent agent contains, for example, a polymer having a perfluoroalkyl group. The liquid-repellent agent can be applied by a method such as air spraying, electrostatic spraying, dip coating, spin coating, roll coating, curtain flow coating, or impregnation.

The thickness of the gas-permeable membrane 3 can be adjusted, for example, in the range of 1 μm or more and 5 mm or less in consideration of the strength and ease of fixation to the internal member 2. The gas permeation rate of the gas-permeable membrane 3 is, for example, 0.1 to 300 sec/100 mL as expressed by the air permeation rate (Gurley permeability) measured according to Method B (Gurley method) of air permeability measurement specified in Japanese Industrial Standards (JIS) L 1096.

The gas-permeable membrane 3 may be joined to the internal member 2. The gas-permeable membrane 3 can be joined to the internal member 2, for example, by any of various welding methods such as thermal welding, ultrasonic welding, and laser welding. The gas-permeable membrane 3 may be joined to the internal member 2 using an adhesive or pressure-sensitive adhesive. The gas-permeable membrane 3 may be disposed at the end portion 11A of the internal member 2 by insert molding of the gas-permeable membrane 3 in conjunction with the internal member 2.

The material of the internal member 2 is commonly an elastic body. The material of the external member 4 is typically a resin. These members can be formed by a commonly-known molding method such as injection molding, compression molding, or powder molding. The internal member 2 and the external member 4 are preferably molded by injection molding because in that case, efficiency of mass production of the ventilation assembly 1A can be improved. Examples of the elastic body that can form the internal member 2 include an elastomer (elastic resin). The elastomer may be a rubber. Examples of the elastomer include nitrile rubber (NBR), ethylene-propylene rubber (EPDM), silicone rubber, fluorine rubber, acrylic rubber, hydrogenated rubber, and various thermoplastic elastomers. Examples of the resin that can form the external member 4 include thermoplastic resins and the above elastomers. Examples of the thermoplastic resin include polyamide (PA) such as nylon, polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polyphenylene sulfide (PPS), polycarbonate (PC), polypropylene (PP), and polyphenylene ether (PPE). The internal member 2 and the external member 4 may be formed of the same material.

The elastic body forming the internal member 2 and/or the resin forming the external member 4 may include an additive, for example, a pigment such as carbon black or titanium white, a reinforcing filler such as glass particles or glass fibers, or a water-repellent agent. A surface of the internal member 2 and/or that of the external member 4 may have at least partially been subjected to the liquid-repellent treatment. The liquid-repellent treatment can be performed, for example, by forming a coating by any of the methods described above as the liquid-repellent treatment method for the gas-permeable membrane 3, electrodeposition coating, or plasma polymerization.

The internal member 2 and/or the external member 4 may include a locking mechanism detachably joining the internal member 2 and the external member 4 together. The locking mechanism is formed of, for example, a claw portion, a screw portion, or a fitting portion.

The housing 51 is formed of, for example, a resin, a metal, or a composite material thereof. The same applies to the projection 52. The resin forming the projection 52 is commonly not an elastic body. Examples of the resin forming the projection 52 include a thermoplastic resin (excluding elastic bodies) and thermosetting resin. Examples of the thermoplastic resin include the various thermoplastic resins mentioned as examples of the resin that can form the external member 4 and acrylonitrile-butadiene-styrene copolymer resin (ABS). The structure of the housing 51 is not limited as long as the projection 52 is included.

Second Embodiment

FIGS. 3A and 3B show a ventilation assembly 1B of a second embodiment. FIG. 3B shows a cross-section B-B of the ventilation assembly 1B shown in FIG. 3A. FIG. 3A shows a cross-section A-O-A of the ventilation assembly 1B shown in FIG. 3B. FIGS. 3A and 3B show a state where the ventilation assembly 1B is fixed to the projection 52 of the housing 51, in other words, the vicinity of the projection 52 of the housing 51 in a ventilation housing including the ventilation assembly 1B fixed to the projection 52. FIG. 4 shows an exploded perspective view of the ventilation assembly 1B shown in FIGS. 3A and 3B. As shown in FIGS. 3A, 3B, and 4, the ventilation assembly 1B is fixed to the tubular projection 52 extending to project from the outer surface 53 of the housing 51 and internally having the first space 59 communicating the inside and the outside of the housing 51.

The ventilation assembly 1B of the second embodiment is the same as the ventilation assembly 1A of the first embodiment, except that the shape of the external member 4 is different. The description common to the first embodiment is omitted.

The external member 4 of the ventilation assembly 1B is in the shape of a cylinder having a bottom. The external member 4 of the ventilation assembly 1B has two or more third projecting portions 43 projecting from the inner peripheral surface 31 toward the interior of the external member 4 when observed along the central axis O. More specifically, the third projecting portions 43 project toward the central axis O from the inner peripheral surface 31. The third projecting portions 43 extend from the end portion 42 of the external member 4 on the opening side to the bottom portion 32. The direction in which the third projecting portions 43 extend is the direction along the central axis O. The third projecting portions 43 connect to the second projecting portions 34 at the bottom portion 32. However, the direction in which the third projecting portions 43 extend and a zone in which the third projecting portions 43 extend and which is between the end portion 42 and the bottom portion 32 are not limited to those in the above example. The third projecting portions 43 and the second projecting portions 34 may not be connected to each other, and the external member 4 may have the second projecting portions 34 and the third projecting portions 43 independent of each other.

The internal member 2 and the external member 4 in the second embodiment are joined to each other by making the outer peripheral surface 19 of the internal member 2 and front end faces 44 of the third projecting portions 43 of the external member 4 abut each other. In the example shown in FIGS. 3A, 3B, and 4, the front end faces 44 of the third projecting portions 43 coincide with the peripheral surface of a virtual column C having the central axis O as its central axis. Because the material of the internal member 2 is commonly the elastic body, the virtual column C commonly has a diameter equal to or smaller than the diameter of the outer peripheral surface 19. However, the front end faces 44 of the third projecting portions 43 may not coincide with the peripheral surface of the virtual column C as long as the internal member 2 and the external member 4 can be joined together by making the outer peripheral surface 19 and the front end faces 44 abut each other. Gaps 6B between the inner peripheral surface 31 of the external member 4 and the outer peripheral surface 19 of the internal member 2 are each a part of the space 5 a. In the example shown in FIGS. 3A, 3B, and 4, the gaps 6B are each surrounded by the inner peripheral surface 31, the outer peripheral surface 19, and the third projecting portions 43.

The external member 4 shown in FIGS. 3A, 3B, and 4 includes twelve third projecting portions 43. The number of third projecting portions 43 in the second embodiment is, for example, six to sixteen.

In the example shown in FIGS. 3A, 3B, and 4, the cross-sections whose areas compose the area S2 _(min) are each surrounded by front ends 49 of the adjacent second projecting portions 34 and on the central axis O side, the inner side 33 of the bottom portion 32 of the external member 4, and the end portion 11A of the internal member 2 (refer to the cross-section 47 in FIG. 4). FIG. 4 shows a part (only the cross-section 47 located between a pair of the adjacent second projecting portions 34) of the cross-sections whose areas compose the area S2 _(min). Because the cross-sections whose areas compose the area S2 _(min) are present between twelve second projecting portions 34, twelve times the area of the cross-section 47 corresponds to the area S2 _(min).

In the example shown in FIGS. 3A, 3B, and 4, the cross-sections whose areas compose the area S2 _(out) are each surrounded by the inner peripheral surface 31 of the external member 4, the outer peripheral surface 19 of the internal member 2, and the third projecting portions 43 (refer to the cross-section 48 in FIG. 3B). FIG. 3B shows a part (only the cross-section 48 located between a pair of the adjacent third projecting portions 43) of the cross-sections whose areas compose the area S2 _(out). Because the cross-sections whose areas compose the area S2 _(out) are present between the twelve second projecting portions 34, twelve times the area of the cross-section 48 corresponds to the area S2 _(out).

Third Embodiment

FIGS. 5A and 5B show a ventilation assembly 1C of a third embodiment. FIG. 5B shows a cross-section B-B of the ventilation assembly 1C shown in FIG. 5A. FIG. 5A shows a cross-section A-O-A of the ventilation assembly 1C shown in FIG. 5B. FIGS. 5A and 5B show a state where the ventilation assembly 1C is fixed to the projection 52 of the housing 51, in other words, the vicinity of the projection 52 of the housing 51 in a ventilation housing including the ventilation assembly 1C fixed to the projection 52. FIG. 6 shows an exploded perspective view of the ventilation assembly 1C shown in FIGS. 5A and 5B. As shown in FIGS. 5A, 5B, and 6, the ventilation assembly 1C is fixed to the tubular projection 52 extending to project from the outer surface 53 of the housing 51 and internally having the first space 59 communicating the inside and the outside of the housing 51.

The ventilation assembly 1C of the third embodiment is the same as the ventilation assembly 1B of the second embodiment, except that the shape of the internal member 2 is different. The description common to the second embodiment is omitted.

In a state where the external member 4 is not joined, the thickness T1 of the internal member 2 of the ventilation assembly 1C increases from the upper end portion (the end portion 11A) of the internal member 2 toward the lower end portion (the end portion 11B) thereof, more specifically, from the end portion 11A to the step 16 adjacent to the thin portion 15. Thus, the internal member 2 has a slope downwardly spreading out as the outer peripheral surface 19 (refer to FIG. 6). In the example shown in FIG. 6, the thickness T1 continuously increases from the upper end portion of the internal member 2 toward the lower end portion thereof, more specifically, from the end portion 11A to the step 16. The way the thickness T1 increases is not limited to the above example, and the thickness T1, for example, may intermittently increase or may partly decrease. In the example shown in FIG. 6, the outer peripheral surface 19 of the internal member 2 forms the peripheral surface of a circular truncated cone whose diameter increases from the upper end portion toward the lower end portion. In a state where the external member 4 is joined (refer to FIGS. 5A and 5B), each of the third projecting portions 43 of the external member 4 compresses a portion of the outer peripheral surface 19 of the internal member 2 formed of the elastic body, the portion being held against the third projecting portion 43, to bite into the outer peripheral surface 19. The front end face 44 of the third projecting portion 43 sinks deeper into the internal member 2 with respect to the position of the outer peripheral surface 19 in a state where the external member 4 is not joined. At the portion where the outer peripheral surface 19 of the internal member 2 is held against each of the third projecting portions 43, the degree to which the third projecting portion 43 bites into the outer peripheral surface 19 increases from the bottom portion 32 of the external member 4 toward the end portion 42 and from the upper end portion (the end portion 11A) of the internal member 2 toward the lower end portion (the end portion 11B) thereof. A combination of the internal member 2 and external member 4 having the above shapes can increase the rate of downward compression between the internal member 2 and the external member 4 at the portion where the two members abut each other, and that makes it possible to more reliably join the external member 4 to the internal member 2. The combination of the internal member 2 and external member 4 having the above shapes can more reliably prevent dropping of the ventilation assembly 1C from the projection 52 because the direction of the force acting on the internal member 2 by joining the external member 4 thereto is the direction perpendicular to the plane of the slope, more specifically, the direction of pressing the internal member 2 toward the outer surface 53 side of the housing 51.

In the ventilation assembly 1C of the third embodiment, the thickness T1 (T1 a) of the internal member 2 at the end portion 11A may be within the above T1 range. In that case, sufficient strength of the internal member 2 can be ensured and, for example, tearing, etc. of the internal member 2 can be reduced at the time of joining the external member 4 to the internal member 2.

In the example shown in FIGS. 5A, 5B, and 6, the shortest length L1 is the sum of the shortest distance along the above slope from the outer periphery 24 of the internal member 2 to the step 16 and the distance in the direction along the central axis O from the step 16 to the ventilation hole 17.

Fourth Embodiment

FIGS. 7A and 7B show a ventilation assembly 1D of a fourth embodiment. FIG. 7B shows a cross-section B-B of the ventilation assembly 1D shown in FIG. 7A. FIGS. 7A and 7B show a state where the ventilation assembly 1D is fixed to the projection 52 of the housing 51, in other words, the vicinity of the projection 52 of the housing 51 in a ventilation housing including the ventilation assembly 1D fixed to the projection 52. FIG. 8 shows an exploded perspective view of the ventilation assembly 1D shown in FIGS. 7A and 7B. As shown in FIGS. 7A, 7B, and 8, the ventilation assembly 1D is fixed to the tubular projection 52 extending to project from the outer surface 53 of the housing 51 and internally having the first space 59 communicating the inside and the outside of the housing 51.

The ventilation assembly 1D of the fourth embodiment is the same as the ventilation assembly 1A of the first embodiment, except that the shapes of the internal member 2 and the external member 4 are different. The description common to the first embodiment is omitted.

The internal member 2 of the ventilation assembly 1D has a rib 18 extending in the peripheral direction on the outer peripheral surface 19. The internal member 2 and the external member 4 are joined together by making the outer peripheral surface 19 of the internal member 2 and the inner peripheral surface 31 of the external member 4 abut each other. Because the material of the internal member 2 is commonly the elastic body, the inner peripheral surface 31 of the external member 4 commonly has a diameter equal to or smaller than the diameter of the outer peripheral surface 19 of the internal member 2. In a state where the internal member 2 and the external member 4 are joined together, the end portion of the external member 4 on the opening side and the rib 18 abut each other.

A gap 6C is provided in the inside of the peripheral wall 37 of the external member 4. The gap 6C is a part of the space 5 a.

A portion of the peripheral wall 37 of the external member 4 and on the central axis O side with respect to the gap 6C is divided into a plurality of beam portions 39 by a plurality of slits 38 extending in the direction along the central axis O. Each of the second projecting portions 34 of the external member 4 is connected to the upper end portion of each of the beam portions 39. By virtue of such a shape, the external member 4 and the ventilation assembly 1D can be reduced in weight.

In the example shown in FIGS. 7A, 7B, and 8, the cross-sections whose areas compose the area S2 _(min) are each surrounded by front ends 49 of the adjacent second projecting portions 34 and on the central axis O side, the inner side 33 of the bottom portion 32 of the external member 4, and the end portion 11A of the internal member 2 (refer to the cross-section 47 in FIG. 8). FIG. 8 shows a part (only the cross-section 47 located between a pair of the adjacent second projecting portions 34) of the cross-sections whose areas compose the area S2 _(min). Because the cross-sections whose areas compose the area S2 _(min) are present between eight second projecting portions 34, eight times the area of the cross-section 47 corresponds to the area S2 _(min).

In the example shown in FIGS. 7A, 7B, and 8, the cross-section whose area composes the area S2 _(out) corresponds to a cross-section of the gap 6C taken along a plane perpendicular to the central axis (refer to the cross-section 48 in FIG. 7B).

In the example shown in FIGS. 7A, 7B, and 8, the shortest length L1 is the sum of the shortest distance from the outer periphery 24 of the internal member 2 to a perimeter 60 at the height of the lower ends of the slits 38 of the external member 4 on the gap 6C side and the distance in the direction along the central axis O from the perimeter 60 and the ventilation hole 17.

Fifth Embodiment

FIGS. 9A and 9B show a ventilation assembly 1E of a fifth embodiment. FIG. 9B shows a cross-section B-B of the ventilation assembly 1E shown in FIG. 9A. FIGS. 9A and 9B show a state where the ventilation assembly 1E is fixed to the projection 52 of the housing 51, in other words, the vicinity of the projection 52 of the housing 51 in a ventilation housing including the ventilation assembly 1E fixed to the projection 52. FIG. 10 shows an exploded perspective view of the ventilation assembly 1E shown in FIGS. 9A and 9B. As shown in FIGS. 9A, 9B, and 10, the ventilation assembly 1E is fixed to the tubular projection 52 extending to project from the outer surface 53 of the housing 51 and internally having the first space 59 communicating the inside and the outside of the housing 51.

The ventilation assembly 1E of the fifth embodiment is the same as the ventilation assembly 1A of the first embodiment, except that the shapes of the internal member 2 and the external member 4 are different. The description common to the first embodiment is omitted.

The internal member 2 of the ventilation assembly 1E has two or more protruding portions 21 projecting from the outer peripheral surface 19 toward the exterior of the internal member 2 when observed along the central axis O of the ventilation assembly 1E. The protruding portions 21 are provided at regular intervals in the peripheral direction of the outer peripheral surface 19. Each of the protruding portions 21 extends in the direction along the central axis O from the one end portion 11A of the internal member 2 to the step 16. However, a zone in which the protruding portions 21 extend in the direction along the central axis O and which is between the one end portion 11A to the other end portion 11B of the internal member 2 is not limited to the above example. In the example shown in FIGS. 9A, 9B, and 10, each of the protruding portions 21 has, on the other end portion 11B side, a portion 23 where the amount of projection from the outer peripheral surface 19 is small.

The internal member 2 and the external member 4 in the fifth embodiment are joined to each other by making peripheral surfaces 22 of the protruding portions 21 of the internal member 2 and the inner peripheral surface 31 of the external member 4 abut each other. In the example shown in FIGS. 9A, 9B, and 10, the peripheral surfaces 22 coincide with the peripheral surface of a virtual column D having the central axis O as its central axis. Because the material of the internal member 2 is commonly the elastic body, the virtual column D commonly has a diameter equal to or larger than the diameter of the inner peripheral surface 31. However, the peripheral surfaces 22 of the protruding portions 21 may not coincide with the peripheral surface of the virtual column D as long as the internal member 2 and the external member 4 can be joined together by making the peripheral surfaces 22 and the inner peripheral surface 31 abut each other. Gaps 6D between the inner peripheral surface 31 of the external member 4 and the outer peripheral surface 19 of the internal member 2 are each a part of the space 5 a. In the example shown in FIGS. 9A, 9B, and 10, the gaps 6D are each surrounded by the inner peripheral surface 31, the outer peripheral surface 19, and the protruding portions 21.

The internal member 2 shown in FIGS. 9A, 9B, and 10 has six protruding portions 21. The number of the protruding portions 21 in the fifth embodiment is, for example, three to eight.

In the example shown in FIGS. 9A, 9B, and 10, the cross-sections whose areas compose the area S2 _(min) are each surrounded by the inner peripheral surface 31 of the external member 4, the outer peripheral surface 19 of the internal member 2, and the protruding portions 21 (refer to the cross-section 47 in FIG. 10). FIG. 10 shows a part (only the cross-section 47 located between a pair of the adjacent protruding portions 21) of the cross-sections whose areas compose the area S2 _(min). Because the cross-sections whose areas compose the area S2 _(min) are present between six protruding portions 21, six times the area of the cross-section 47 corresponds to the area S2 _(min).

In the example shown in FIGS. 9A, 9B, and 10, the cross-sections whose areas compose the area S2 _(out) are each surrounded by the inner peripheral surface 31 of the external member 4 at the end portion 42 of the external member 4 on the opening side, the outer peripheral surface 19 of the internal member 2, and the protruding portions 21 (refer to the cross-section 48 in FIG. 10). FIG. 10 shows a part (only the cross-section 48 located between a pair of the adjacent protruding portions 21) of the cross-sections whose areas compose the area S2 _(out). Because the cross-sections whose areas compose the area S2 _(out) are present between the six protruding portions 21, six times the area of the cross-section 48 corresponds to the area S2 _(out).

In the example shown in FIGS. 9A, 9B, and 10, the external member 4 has claws 45 projecting toward the interior of the external member 4, more specifically, toward the central axis O, at the ends on the end portion 42 side on the opening side. In a state where the internal member 2 and the external member 4 are joined together, the claw 45 is locked to the portion 23 of the internal member 2 and functions as a locking mechanism detachably joining the internal member 2 and the external member 4 together. The internal member 2 and the external member 4 can be more reliably joined together by the locking mechanism, more specifically, by locking the claw 45 to the portion 23. For example, dropping of the external member 4 from the internal member 2 can be prevented at the time of fixation of the ventilation assembly 1E to the projection 52 of the housing 51.

Sixth Embodiment

FIGS. 11A and 11B show a ventilation assembly 1F of a sixth embodiment. FIG. 11B shows a cross-section B-B of the ventilation assembly 1F shown in FIG. 11A. FIG. 11A shows a cross-section A-O-A of the ventilation assembly 1F shown in FIG. 11B. FIGS. 11A and 11B show a state where the ventilation assembly 1F is fixed to the projection 52 of the housing 51, in other words, the vicinity of the projection 52 of the housing 51 in a ventilation housing including the ventilation assembly 1F fixed to the projection 52. FIG. 12 shows an exploded perspective view of the ventilation assembly 1F shown in FIGS. 11A and 11B. As shown in FIGS. 11A, 11B, and 12, the ventilation assembly 1F is fixed to the tubular projection 52 extending to project from the outer surface 53 of the housing 51 and internally having the first space 59 communicating the inside and the outside of the housing 51.

The ventilation assembly 1F of the sixth embodiment is the same as the ventilation assembly 1A of the first embodiment, except that the shape of the external member 4 is different. The description common to the first embodiment is omitted.

The external member 4 of the ventilation assembly 1F has a through hole 50 penetrating the peripheral wall 37 of the external member 4 and connecting the outside of the ventilation assembly 1F and the second space 5. An opening of the through hole 50 on an outer surface of the external member 4 is the end portion (the ventilation hole 17) of the ventilation path on the outside side of the ventilation assembly 1F. The through hole 50 may penetrate the bottom portion 32 of the external member 4 and/or the peripheral wall 37 of the external member 4, and may be arranged through both the bottom portion 32 and the peripheral wall 37. The shortest length L1 extends through the through hole 50. In the sixth embodiment, the shortest length L1 can be shorter and, compared to conventional ventilation assemblies, the water vapor permeation properties of the ventilation assembly 1F can be increased further. In the example shown in FIGS. 11A, 11B, and 12, the shortest length L1 is the shortest distance from the outer periphery 24 of the internal member 2 to a portion of the ventilation hole 17, the portion being located at the outer peripheral surface 40 of the external member 4.

In the external member 4 of the sixth embodiment, the number of the through holes 50 is not limited to the above example. For example, the number of the through holes 50 is four in the example shown in FIGS. 11A, 11B, and 12. The number of the through holes 50 may be two to six.

In the example shown in FIGS. 11A, 11B, and 12, the cross-sections whose areas compose the area S2 _(min) are each an opening face (an opening face at the inner peripheral surface 31 of the external member 4) of the through hole 50 of the external member 4, the opening face being viewed along the ventilation direction (refer to the cross-section 47 in FIG. 12). FIG. 12 shows a part (only the cross-section 47 corresponding to one of the through holes 50) of the cross-sections whose areas compose the area S2 _(min). Because the cross-sections whose areas compose the area S2 _(min) each correspond to one of the four through holes 50, four times the area of the cross-section 47 corresponds to the area S2 _(min).

EXAMPLES

<Moisture Permeation Test 1 of Ventilation Assembly and Ventilation Housing>

Example 1

An internal member 2 having the shape shown in FIG. 13A was produced by injection molding using an olefin-based thermoplastic elastomer (MILASTOMER (registered trademark) manufactured by Mitsui Chemicals, Inc.; hardness: 71; density: 880 kg/m³) as a material. The obtained internal member 2 had a maximum thickness of 2.4 mm, a minimum thickness of 1.1 mm, an outer diameter of 12 mm at a portion having the maximum thickness, an outer diameter of 10 mm at a portion having the minimum thickness, an inner diameter of 7.5 mm, and a height H1 of 8.0 mm. The internal member 2 of FIG. 13A had the same shape as that of the internal member 2 of FIGS. 3A, 3B, and 4, except for having a projecting portion (a bridge) 62 projecting into the internal space of the internal member 2 at the end portion 11A.

An external member 4 having the shape shown in FIGS. 13A and 13B was produced by injection molding using polypropylene (manufactured by Japan Polypropylene Corporation) as a material. The obtained external member 4 had a maximum thickness of 2.5 mm, a minimum thickness of 0.6 mm, an outer diameter of 16 mm, an inner diameter of 11.1 mm at a portion having the maximum thickness, an inner diameter of 13.3 mm at a portion having the minimum thickness, and a height of 9.0 mm. The external member 4 of FIGS. 13A and 13B had the same shape as that of the external member 4 of FIGS. 3A, 3B, and 4, except for having the claw 45 projecting toward the central axis O at the end of the third projecting portion 43 and on the end portion 42 side. In FIGS. 13A and 13B, the internal member 2 and the external member 4 are viewed from the bottom (the opening side of the external member 4).

Next, a laminate (TEMISH “NTF1026-L01” manufactured by Nitto Denko Corporation; gas permeation amount: 50 cm³/min) of a stretched porous PTFE membrane and a non-woven fabric made of PE/PET composite fibers was used as a material and was punched to give a 12-mm-diameter circular piece. A gas-permeable membrane 3 was thus produced. Then, the gas-permeable membrane 3 was disposed so as to completely cover the through hole 14 of the internal member 2. The gas-permeable membrane 3 was welded to the internal member 2 by compression bonding and heating at a temperature of 200° C. and a pressure of 20 N for 2 seconds. Then, the internal member 2 to which the gas-permeable membrane 3 was welded was press-fitted (inserted) into the external member 4 to obtain a ventilation assembly.

A housing lid 61 shown in FIGS. 14A and 14B and including the tubular projection 52 internally having the first space 59 was produced using a hard resin “Vero Black Plus (RGD875)” as a material and a 3D printer (Objet30 Prime). FIG. 14B shows a cross-section B-B shown in FIG. 14A. The projection 52 had an outer diameter of 8.5 mm, an inner diameter of 5.0 mm, and a height H2 of 8.0 mm. Next, the projection 52 of the housing lid 61 was inserted (inserted until the end portion of the internal member 2 on the lower side came into contact with the housing 61) in the opening (the opening at the end portion on the lower side) of the internal member 2 of the ventilation assembly to prepare a ventilation assembly-attached housing lid including the ventilation assembly fixed to the projection 52.

An amount of 42 g of water was held in a moisture permeation cup (having a 60-mm-diameter opening and an inner diameter of 60 mm as specified in Japanese Industrial Standards (JIS) L 1099 A-2 (water method)) having been left to stand in a thermo-hygrostat at a humidity of 50% and a temperature of 40° C. The ventilation assembly-attached housing lid was disposed on and attached to the opening portion of the cup in such a manner that the entire opening face of the cup was completely covered. The projection 52 and the ventilation assembly were exposed to the outside of the cup. In the attached state, the interval between the water surface and the lower surface of the housing lid 61 was 10 mm and the moisture permeation area of the ventilation assembly was 44 mm². Then, the cup was left to stand in the above thermo-hygrostat for 1 hour. After that, the cup was taken out of the thermo-hygrostat and, together with the ventilation assembly-attached housing lid, measured for a mass W1 (g). Subsequently, after left to stand in the above thermo-hygrostat for 24 hours, the cup was taken out again and, together with the ventilation assembly-attached housing lid, measured for a mass W2 (g). The difference between the masses measured for the cup before and after the cup was left to stand in the thermo-hygrostat for the second time was defined as A (g) (=W1−W2), and the area of the opening face of the cup was defined as B (m²). The moisture permeation rate was calculated by the following equation (1) as the moisture permeation performance of the ventilation housing.

Moisture permeation rate[gm ⁻² h ⁻¹]=A/B/24  (1)

Table 1 shows the result of measuring the moisture permeation rate. The term “insertion depth of external member” in Table 1 refers to the central axial length of a portion of the internal member, the portion being covered by the external member when observed in the direction perpendicular to the central axis of the ventilation assembly. The term “inside-outside contact length” refers to the central axial length of a portion where the external member and the internal member are in contact with each other when observed in the direction perpendicular to the central axis of the ventilation assembly. The term “ventilation distance” refers to the distance determined by adding the height H1 of the internal member and the insertion depth (corresponding the length L1) of the external member. The “ventilation distance” substantially corresponds to the distance from the inside of the housing to an exit of the ventilation assembly.

Examples 2 to 5

The moisture permeation test was performed in the same manner as in Example 1, except that the height H1 of the internal member 2, the height H2 of the projection 52, the gas permeation amount of the gas-permeable membrane 3, the height of the external member 4, the insertion depth of the external member 4, and the inside-outside contact length were changed to the values shown in Table 1. Table 1 shows the results of measuring the moisture permeation rate.

Comparative Example 1

The moisture permeation test was performed in the same manner as in Example 1, except that the shapes of the internal member 2 and the external member 4 were changed to those shown in FIGS. 15A and 15B. Table 1 shows the result of measuring the moisture permeation rate. In Comparative Example 1, the height H1 of the internal member 2, the height H2 of the projection 52, the gas permeation amount of the gas-permeable membrane 3, the height of the external member 4, the insertion depth of the external member 4, and the inside-outside contact length are as shown in Table 1. The internal member 2 of FIG. 15A had the same shape as that of the internal member 2 of FIGS. 9A, 9B, and 10, except that the number of the protruding portions 21 is four. The external member 4 of FIGS. 15A and 15B had the same shape as that of the external member 4 of FIGS. 9A, 9B, and 10, except that the external member 4 of FIGS. 15A and 15B had no claw 45, that the end portion 42 on the opening side was located lower than the step 16 when viewed in the direction perpendicular to the central axis of the ventilation assembly, and that the external member 4 of FIGS. 15A and 15B had three second projecting portions 34 projecting to extend from the inner peripheral surface 31 toward the central axis on the inner side 33 of the bottom portion 32. In FIGS. 15A and 15B, the internal member 2 and the external member 4 are viewed from the bottom.

TABLE 1 Gas Height Height permeation Insertion Inside- H1 of H2 of amount of Height of depth of outside Moisture internal tubular gas-permeable external external contact Ventilation permeation member projection membrane member member length distance rate [mm] [mm] [cm³/min] [mm] [mm] [mm] [mm] [gm⁻²h⁻¹] Example 1 8 8 50 9 7 5.5 15 60.6 Example 2 10 5 3 3 11 69.1 Example 3 7 5 5 13 66.7 Example 4 9 7 5.5 15 55.6 Example 5 8 13000 15 59.4 Comparative 12 10 50 12 10 5.05 22 49.6 Example 1

For Examples 1 to 5 and Comparative Example 1, FIG. 16 shows a graph on which a relation between the moisture permeation rates and the ventilation distances is plotted. In the graph, Examples 1 to 4 in which the height H1 of the internal member was 8.0 mm and the gas permeation amount of the gas-permeable membrane was 50 cm³/min are plotted as black circles (●). Example 5 in which the height H1 of the internal member was 8.0 mm and the gas permeation amount of the gas-permeable membrane was 13000 cm³/min is plotted as a black triangle (▴). Comparative Example 1 in which the height H1 of the internal member was 12 mm and the gas permeation amount of the gas-permeable membrane was 50 cm³/min is plotted as a circle (∘). As shown in FIG. 16, the approximately 260-fold difference between the gas permeation amounts of the gas-permeable membranes of each of Examples 1 to 4 and Example 5 does not cause a great difference in the moisture permeation rate, compared to the difference between the ventilation distances thereof. This clearly indicates a great dependence of the moisture permeation rate on the ventilation distance. Additionally, in Comparative Example 1 in which the height H1 of the internal member is 12 mm and the height of the external member is also 12 mm, the moisture permeation rate tends to be low on the whole due to the relatively long ventilation distance. On the other hand, in Examples 1 to 5 in which the height H1 of the internal member is 8.0 mm, the moisture permeation rates tend to be high on the whole.

<Moisture Permeation Test 2 of Ventilation Assembly and Ventilation Housing>

[Preparation of Ventilation Assembly]

A ventilation assembly A (Example 6) in which the height H1 of the internal member was 8.0 mm, the height of the external member was 9.0 mm, and the insertion depth of the external member was 7.0 mm was obtained in the same manner as in Example 1.

A ventilation assembly B (Example 7) was obtained in the same manner as in Example 1, except that the shapes of the internal member 2 and the external member 4 were changed to those shown in FIGS. 15A and 15B.

A ventilation assembly C (Example 8) was obtained in the same manner as in Example 1, except that the shapes of the internal member 2 and the external member 4 were changed to those shown in FIGS. 17A and 17B. The internal member 2 of FIG. 17A had the same shape as that of the internal member 2 of FIGS. 7A, 7B, and 8, except for having no rib 18. The external member 4 of FIGS. 17A and 17B had the same shape as that of the external member 4 of FIGS. 7A, 7B, and 8, except that the positions and shapes of the second projecting portions 34 were different. The gap 6C which is a part of the space 5 a was provided in the inside of the peripheral wall of the external member 4. In FIGS. 17A and 17B, the internal member 2 and the external member 4 are viewed from the bottom.

A ventilation assembly D (Example 9) was obtained in the same manner as in Example 1, except that the shapes of the internal member 2 and the external member 4 were changed to those shown in FIGS. 18A and 18B. The internal member 2 of FIG. 18A had the same shape as that of the internal member 2 of FIGS. 7A, 7B, and 8. The external member 4 of FIGS. 18A and 18B had the same shape as that of the external member 4 of FIGS. 7A, 7B, and 8. In FIGS. 18A and 18B, the internal member 2 and the external member 4 are viewed from the bottom.

A ventilation assembly E (Example 10) was obtained in the same manner as in Example 1, except that the shapes of the internal member 2 and the external member 4 were changed to those shown in FIGS. 19A and 19B. The internal member 2 of FIG. 19A had the same shape as that of the internal member 2 of FIGS. 9A, 9B, and 10, except that the number of the protruding portions 21 was three. The external member 4 of FIGS. 19A and 19B had the same shape as that of the external member 4 of FIGS. 9A, 9B, and 10, except that the external member 4 of FIGS. 19A and 19B had no claw 45, that the end portion 42 on the opening side was located lower than the step 16 when viewed in the direction perpendicular to the central axis of the ventilation assembly, and that the external member 4 of FIGS. 19A and 19B had three second projecting portions 34 projecting to extend from the inner peripheral surface 31 toward the central axis on the inner side 33 of the bottom portion 32. In FIGS. 19A and 19B, the internal member 2 and the external member 4 are viewed from the bottom.

In the ventilation assemblies B to E, the height H1 of the internal member, the height of the external member, and the insertion depth of the external member were the same as those in the ventilation assembly A.

The ventilation assemblies were each measured for the area S2 _(min) of cross-sections having the smallest areas, the cross-sections of the second space each taken along a plane perpendicular to the ventilation direction in the ventilation path. For the cross-sections having the smallest areas, the cross-section 47 shown in some figures can be referred to. The figures show a part of the cross-sections having the smallest areas, which is the smallest unit of the cross-sections having the smallest areas, as the cross-section 47. For the ventilation assemblies, the area S2 _(min) of the cross-sections having the smallest areas was twelve times (ventilation assembly A), three times (ventilation assembly B), six times (ventilation assembly C), and eight times (ventilation assembly D) the area of the cross-section 47. The measurement operation was specifically as follows. It should be noted that the area S2 _(min) of the ventilation assembly E was the area S2 _(out) to be described. The total area of cross-sections each taken at a position where the total area is the second smallest to the area S2 _(out) is three times the area of the cross-section 47.

A picture of the external member 4 was taken in such a manner that the cross-sections having the smallest areas were included. Next, the obtained image was imported in image analysis software ImageJ, which can measure dimensions in images, and the scale was set for the image data so as to match the dimensions (actual measured values) of the ventilation assembly. Then, the dimensions of the cross-sections having the smallest areas were measured using the image analysis software, and the area S2 _(min) was calculated. Table 2 shows the result of calculating S2 _(min). As examples, FIG. 20 shows images used to measure S2 _(min) of the ventilation assemblies A and B. In FIG. 20, (a) shows the ventilation assembly A and (b) shows the ventilation assembly B. A white line 71 in each image corresponds to one of the cross-sections having the smallest areas.

Next, the ventilation assemblies were each measured for the total area S2 _(out) of a plane(s) being a cross-section(s) each taken at a position where the second space is the narrowest when the second space is observed from the other end portion side (the lower side) along the central axis of the ventilation assembly. The measurement operation was specifically as follows.

A picture of the bottom face of each of the ventilation assemblies was taken. Then, the obtained image was imported in image analysis software ImageJ. The image resolution was set to 8 bits, the contrast was adjusted so that the end portion of the ventilation assembly on the bottom side could be clearly shown, and the scale was set for the image data so as to match the dimensions (actual measured values) of the ventilation assembly. Next, a threshold for binarization was set so that only a plane(s) being a cross-section(s) each taken at a position where the ventilation path is the narrowest would be extracted, and an image in which only the end portion was shown in black was created. A portion which was not the end portion but turned black was deleted to complete the image. As examples, FIG. 21 shows images used to measure S2 _(out) of the ventilation assemblies A and B and post-binarization images of the ventilation assemblies A and B. In FIG. 21, (a) shows the ventilation assembly A and (b) shows the ventilation assembly B. FIG. 22 shows post-binarization images of the ventilation assemblies. Subsequently, the area of the black portion in the image was measured using the image analysis software, and the area S2 _(out) was calculated. Table 2 shows the results of calculating S2 _(out).

In the same manner as in the above-described <Moisture permeation test 1 of ventilation assembly and ventilation housing>, a ventilation assembly-attached housing lid was prepared with each of the ventilation assemblies and subjected to the moisture permeation test. Table 2 shows the results of measuring the moisture permeation rate. The projection 52 had an outer diameter of 8.5 mm, an inner diameter of 5.0 mm, and a height of 6.0 mm. The cross-sectional area S1 of the first space taken along a plane perpendicular to the central axis of the projection 52 was 19.6 mm².

TABLE 2 Moisture Area Area permeation Ventilation Area S1 S2_(min) S2_(out) Ratio Ratio rate assembly [mm²] [mm²] [mm²] S2_(min)/S1 S2_(out)/S1 [gm⁻²h⁻¹] Example 6 A 19.6 21.7 44.1 1.1 2.2 57.5 Example 7 B 23.9 26.7 1.2 1.4 49.0 Example 8 C  6.3 47.7 0.3 2.4 42.4 Example 9 D 22.4 50.7 1.1 2.6 68.8 Example 10 E 19.2 19.2 1.0 1.0 42.4 *(25.4)  *(1.3)  *The area S2_(min) of the ventilation assembly E is equal to the area S2_(out) thereof. The values in the parentheses respectively represent the total area of cross-sections each taken at a position where the total area is the second smallest to the area S2_(out) and the ratio of the total area to S1.

For Examples 6 to 10, FIG. 23 shows a graph on which a relation between the ratios S2 _(out)/S1 and the moisture permeation rates is plotted.

<Pull-Out Test for Internal Member>

Reference Example 1

An internal member 2 having the shape shown in FIG. 15A was produced by injection molding using an olefin-based thermoplastic elastomer (MILASTOMER (registered trademark) manufactured by Mitsui Chemicals, Inc.; hardness: 71; density: 880 kg/m³) as a material. The obtained internal member 2 had a thickness of 4.2 mm at a portion having the protruding portion 21, a thickness of 2.3 mm at a portion not having the protruding portion 21 (a non-protruding portion), an outer diameter of 16 mm at a portion having the protruding portion 21, an outer diameter of 12 mm at a non-protruding portion, an inner diameter of 7.5 mm, and a height H1 of 6.0 mm.

Next, a projection 52 made of polypropylene (PP) was prepared as the tubular projection 52 that can be included in a housing (refer to FIG. 24). The projection 52 had an outer diameter of 8.5 mm, an inner diameter of 5.0 mm, and a height H2 of 6.0 mm.

A hole was made with a 0.5-mm-diameter pin at an upper portion (on the side opposite to the side from which the projection was to be inserted) of the internal member 2, and a clip was passed through the hole. Then, the projection (height: 6.0 mm) was inserted to the end of the internal member (height: 6.0 mm).

Next, the clip was fixed to one grip of a tensile tester (Autograph AGS-X manufactured by Shimadzu Corporation), and the projection was fixed to the other grip in such a manner that the direction in which the projection had been inserted in the internal member 2 was perpendicular to a displacement direction of the tensile tester. After that, a tensile test was performed at a tensile speed of 200 mm/min. A test in which the projection 52 is pulled out from the internal member 2 was thus performed (refer to FIG. 24). FIG. 25 shows an SS curve obtained from the tensile test. The maximum load value on the SS curve was defined as the pullout force (horizontal pullout force) of the internal member 2. Table 3 shows the result of measuring the pullout force.

Reference Examples 2 to 29

A tensile test (pullout test for internal member) was performed in the same manner as in Reference Example 1, except that the height H1 of the internal member 2 and the height H2 of the projection 52 were changed to the values shown in Table 3. Table 3 shows the results of measuring the pullout force.

TABLE 3 Height Height H1 of H2 of Pull- internal projec- Ratio out member tion H1/ force Phenomenon caused [mm] [mm] H2 [N] by tensile test Reference 6 6 1.0 44.1 Internal member not Example 1 pulled apart and broken Reference 5 1.2 22.7 Internal member pulled Example 2 apart Reference 4 1.5 11.5 Internal member pulled Example 3 apart Reference 3 2.0 0.5 Internal member pulled Example 4 apart Reference 7 7 1.0 34.8 Internal member not Example 5 pulled apart and broken Reference 6 1.2 31.3 Internal member pulled Example 6 apart Reference 5 1.4 22.2 Internal member pulled Example 7 apart Reference 4 1.8 9.6 Internal member pulled Example 8 apart Reference 2 3.5 2.4 Internal member pulled Example 9 apart Reference 8 8 1.0 42.6 Internal member not Example 10 pulled apart and broken Reference 6 1.3 25.8 Internal member pulled Example 11 apart Reference 5 1.6 19.4 Internal member pulled Example 12 apart Reference 4 2.0 7.6 Internal member pulled Example 13 apart Reference 2 4.0 3.4 Internal member pulled Example 14 apart Reference 9 9 1.0 42.6 Internal member not Example 15 pulled apart and broken Reference 8 1.1 44.4 Internal member not Example 16 pulled apart and broken Reference 6 1.5 24.4 Internal member pulled Example 17 apart Reference 4 2.3 8.5 Internal member pulled Example 18 apart Reference 2 4.5 2.7 Internal member pulled Example 19 apart Reference 10 10 1.0 48.4 Internal member not Example 20 pulled apart and broken Reference 8 1.3 40.8 Internal member not Example 21 pulled apart and broken Reference 6 1.7 24.8 Internal member pulled Example 22 apart Reference 4 2.5 5.6 Internal member pulled Example 23 apart Reference 2 5.0 3.2 Internal member pulled Example 24 apart Reference 12 10 1.2 41.5 Internal member not Example 25 pulled apart and broken Reference 8 1.5 41.0 Internal member pulled Example 26 apart Reference 6 2.0 19.2 Internal member pulled Example 27 apart Reference 4 3.0 6.0 Internal member pulled Example 28 apart Reference 2 6.0 1.9 Internal member pulled Example 29 apart

For Reference Examples in which the internal members 2 were pulled apart without being broken, FIG. 26 shows a graph on which a relation between the ratios H1/H2 and the pullout forces is plotted. The values in the legend of the graph represent the heights H1 of the internal members 2.

<Pullout Test for External Member>

Reference Example 30

An internal member 2 having the shape shown in FIG. 15A was produced by injection molding using an olefin-based thermoplastic elastomer (MILASTOMER (registered trademark) manufactured by Mitsui Chemicals, Inc.; hardness: 71; density: 880 kg/m³) as a material. The obtained internal member 2 had a thickness of 4.2 mm at a portion having the protruding portion 21, a thickness of 2.3 mm at a portion not having the protruding portion 21 (a non-protruding portion), an outer diameter of 16 mm at a portion having the protruding portion 21, an outer diameter of 12 mm at a non-protruding portion, an inner diameter of 7.5 mm, and a height H1 of 6.0 mm.

An external member 4 having the shape shown in FIGS. 15A and 15B was produced by injection molding using polypropylene (manufactured by Japan Polypropylene Corporation) as a material. The obtained external member 4 had a thickness of 1.0 mm, an outer diameter of 17.5 mm, an inner diameter of 15.6 mm, and a height of 12 mm.

Next, a projection 52 made of polypropylene (PP) was prepared as the tubular projection 52 that can be included in a housing (refer to FIG. 24). The projection had an outer diameter of 8.1 mm, an inner diameter of 5.0 mm, and a height H2 of 10 mm.

Next, a hole was made at the bottom portion 32 (on the side opposite to the side from which the internal member 2 was to be inserted) of the external member 4, and a screw was passed through the hole. Then, the internal member 2 was press-fitted (inserted) into the external member 4 (insertion depth of external member 4: 10 mm) to obtain a ventilation assembly. The projection was inserted in the internal member 2 in such a manner that the projection (height: 10 mm) was pushed all the way in the ventilation assembly.

Next, the screw was fixed to one grip of a tensile tester (Autograph AGS-X manufactured by Shimadzu Corporation), and the projection was fixed to the other grip in such a manner that a displacement direction of the tensile tester coincided with the direction in which the projection had been inserted in the ventilation assembly. After that, a tensile test was performed at a tensile speed of 200 mm/min. A test in which the external member 4 is pulled out from the ventilation assembly was thus performed. FIG. 27 shows examples of SS curves obtained from the tensile test. The maximum load values on the SS curves were defined as the pullout forces of the external members 4. Table 4 shows the results of measuring the pullout force. The SS curves of Reference Examples Nos. 31, 32, 33, 34, and 35 are shown in order of decreasing maximum load values.

Reference Examples 31 to 41

A tensile test (pullout test for external member) was performed in the same manner as in Reference Example 30, except that the outer diameter of the projection, the height of the external member, and the insertion depth of the external member were changed to the values shown in Table 4. Table 4 shows the results of measuring the pullout force. The terms “insertion depth of external member” and “inside-outside contact length” in Table 4 are as described in <Moisture permeation test 1 of ventilation assembly and ventilation housing>.

TABLE 4 Outer Insertion Height of diameter Height of depth of Inside-outside Reference internal Height of of external external contact Pullout Example member projection projection member member length force No. [mm] [mm] [mm] [mm] [mm] [mm] [N] 30 10 5.5 31.40 31 9 5.5 32.90 32 8.1 12 8 5.5 27.69 33 7 5.5 22.45 34 6 5.5 16.93 35 12 10 5 5 9.87 36 10 5.5 37.86 37 9 5.5 36.31 38 8.5 12 8 5.5 32.46 39 7 5.5 27.28 40 6 5.5 19.36 41 5 5 9.19

For Reference Examples, FIG. 28 shows a graph on which a relation between the insertion depths of the external members and the pullout forces is plotted. The values in the legend in FIG. 28 represent the outer diameters of the projections. For Examples 2 to 4 in the above-described <Moisture permeation test 1 of ventilation assembly and ventilation housing>, FIG. 29 shows a graph on which a relation between the insertion depths of the external members and the moisture permeation rates is plotted. The value in the legend in FIG. 29 represents the outer diameters of the projections.

INDUSTRIAL APPLICABILITY

The ventilation assembly and the ventilation housing of the present invention can be used in the same applications as conventional ventilation assemblies and ventilation housings. 

1. A ventilation assembly to be fixed to a tubular projection extending to project from an outer surface of a housing and internally having a first space communicating the inside and the outside of the housing, the ventilation assembly comprising: an internal member being a tubular body having an opening at a first end portion and an opening at a second end portion; a gas-permeable membrane covering the opening at the first end portion of the internal member; and an external member being a tubular body having a bottom, the external member being joined to the internal member with the internal member inserted in the interior of the external member from the first end portion side, wherein the ventilation assembly is to be fixed to the projection with the projection inserted in the opening at the second end portion of the internal member to make an inner peripheral surface of the internal member and an outer peripheral surface of the projection abut each other, the ventilation assembly has a second space serving as a ventilation path connecting the gas-permeable membrane and the outside of the ventilation assembly in at least one selected from the inside of the internal member, the inside of the external member, and an interspace between the internal member and the external member joined together, and a total length of a height of the internal member and a shortest length in the second space from an outer periphery of the internal member at the first end portion to an end portion of the ventilation path on the outside side is 6.0 mm or more and 20 mm or less.
 2. The ventilation assembly according to claim 1, wherein when the ventilation assembly is observed in a direction perpendicular to a central axis of the ventilation assembly, a length of a portion of the internal member in a direction along the central axis is 6.0 mm or more and 8.0 mm or less, the portion being covered by the external member.
 3. The ventilation assembly according to claim 1, wherein the external member has a through hole penetrating a bottom portion of the external member and/or a peripheral wall of the external member and connecting the outside of the ventilation assembly and the second space, and the shortest length in the second space extends through the through hole.
 4. The ventilation assembly according to claim 3, wherein the through hole is arranged through both the bottom portion of the external member and the peripheral wall of the external member.
 5. The ventilation assembly according to claim 1, wherein the external member and/or the internal member has a locking mechanism detachably joining the external member and the internal member together.
 6. A ventilation housing comprising: a housing; and a ventilation assembly, wherein the housing comprises a tubular projection extending to project from an outer surface of the housing and internally having a first space communicating the inside and the outside of the housing, the ventilation assembly is the ventilation assembly according to claim 1, and the ventilation assembly is fixed to the projection with the projection inserted in the internal member through the opening at the second end portion of the internal member to make an inner peripheral surface of the internal member and an outer peripheral surface of the projection abut each other.
 7. The ventilation housing according to claim 6, wherein a ratio S2 _(min)/S1 between an area S1 of a cross-section of the first space taken along a plane perpendicular to a central axis of the projection and a smallest total area S2 _(min) determined by comparison of values of different total areas determined at different distances from the gas-permeable membrane is 1.0 or more, the total areas each being determined for a cross-section of the second space taken along a plane perpendicular to a ventilation direction in the ventilation path, the cross-section being located at a certain distance from the gas-permeable membrane.
 8. The ventilation housing according to claim 6, wherein a ratio S2 _(out)/S1 between an area S1 of a cross-section of the first space taken along a plane perpendicular to a central axis of the projection and a total area S2 _(out) of a plane consisting of a cross-section of the second space taken at a position where the second space is the narrowest when the second space is observed from the second end portion side along a central axis of the ventilation assembly is 1.0 or more. 